The possibility of any new gun control laws passing through the legislature is almost nil. When I explain this to people, their reaction is "well, then the President's just going to do it through an executive order! ZOMG!"

That's not how it works.

Executive orders exist for the President to clarify or facilitate enforcement of existing laws. They are not meant to enact new ones. The Executive branch does not have the power to create legislation.

So, what is an executive order? We don't really know, as they aren't specifically defined in the Constitution.

Authority for them is vaguely attributed to Article II, Section 5, which states the President "shall take Care that the Laws be faithfully executed." They're a mechanism for execution, not creation.

The Supreme Court has come down on Presidents who've tried to overstep their authority via EO's before. They spoke on the matter in 1952, finding that President Truman's order placing steel mills under government control overstepped his authority. In 2005, the Court ruled in Hamdan v. Rumsfeld that President Bush lacked the authority to enact war tribunals via such orders.

It's unlikely the current White House would try to enact new regulations via executive order, especially with Heller and McDonald being the 800lb gorillas in the living room. Doing so would trigger a court challenge that would not only overturn the ordinance in question, it would set further limits on what could be done with such orders.

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Sometimes it’s nice not to destroy the world for a change.
--Randall Munroe